L-carnitine is an important, naturally occurring amino acid structure that plays a number of roles in the body. While this compound can be obtained from a variety of food sources—most notably red meats—the body is able to produce it, primarily in the kidneys, liver, and brain. L-carnitine helps in the process of energy production, by transporting fatty acids into cellular mitochondria so these fats can be burned for energy.
Certain disorders and advanced age can cause a deficiency of L-carnitine. In such cases, supplementing with the compound can have positive effects on overall health. Research also suggests that L-carnitine can be beneficial in supporting heart health, metabolism function, and neural disorders associated with aging. To better understand this nutrient, we’ll take a closer look at the role it plays in key systems of the body.1
What Is L-Carnitine?
Carnitine is the general name for a few key compounds in the body that include L-carnitine. It’s synthesized in the body from two amino acids, lysine and methionine. By transporting fatty acids into cells, the powerhouse “cellular engines” known as the mitochondria can then convert fat into energy. It’s for this reason that L-carnitine plays an important role in metabolism.
There are other types of carnitine, which are used for different applications. These include:
- Acetyl-L-carnitine - This dietary supplement form of carnitine is most commonly used to help combat neuroinflammation, especially in neurodegenerative diseases like dementia.2
- Propionyl-L-carnitine - Commonly used in those with circulatory issues—like high blood pressure—this form of carnitine may increase nitric oxide, improving blood flow.3
- L-carnitine L-tartrate - This form of carnitine is often used in supplements for sports and exercise. One study showed that this supplement reduced muscle soreness and metabolic stress after exercise.4
- D-carnitine - This form may decrease other more beneficial forms of carnitine. It’s known as the optimal isomer (mirror image) of L-carnitine and may cause a deficiency in the body.5
How L-Carnitine Works
Carnitine is known as a conditionally essential nutrient. This means that the body usually makes enough of this compound, but some may need supplements if their body does not make adequate amounts. Additionally, depending on overall health, more or less L-carnitine may be needed by the body at a given time.
Aside from being synthesized from amino acids in the body, a variety of food sources contain L-carnitine. 75% of carnitine in humans comes from the diet, with the highest concentration found in red meat. However, because the body can make L-carnitine on its own, even vegetarians that avoid animal products usually have enough of this nutrient. Since their bodies are used to a low-carnitine diet, the bioavailability of L-carnitine is higher in vegetarians than meat eaters.
L-carnitine works by transporting fatty acids into the mitochondria of various types of cells, where they then burn this fuel into energy. By balancing the energy across cells, L-carnitine contributes to the proper function of both skeletal and cardiac muscles. It also helps regular metabolism, enhancing how cells use carbohydrates for fuel.1
What L-Carnitine Is Used For
There are a variety of uses for L-carnitine supplementation, though some areas need more research to verify efficacy. Aside from two types of carnitine deficiency, most supplementation is used in cases of acquired carnitine deficiency or to support overall health.
Obesity And Weight Loss
Some weight loss supplements contain L-carnitine, though more research is needed to verify results. In one study analyzing nine clinical research trials, carnitine supplements resulted in an average loss of 2.9 lbs. Most of those in these studies were either overweight, obese, or older, so more research is needed on those in lower BMI (body mass index) categories and of younger ages. Additional studies showed that L-carnitine supplementation could help with insulin resistance.1,6
Exercise And Muscle Recovery
L-carnitine supplements are commonly used by athletes and bodybuilders as a pre-or post-workout supplement. However, there have been no concrete research studies linking L-carnitine supplementation to better athletic performance in healthy participants.7
While L-carnitine doesn’t appear to enhance exercise ability directly, it has been shown to aid in muscle recovery. One study examines untrained subjects undergoing eccentric effort of the quadriceps. After 7 weeks, subjects felt less pain and tenderness in their muscles with L-carnitine supplementation vs those with a placebo. This is likely because of the role L-carnitine plays in the metabolism of damaged muscle tissues.8
Because of the effects of L-carnitine on insulin resistance and metabolism, research suggests it may be helpful in improving overall health in diabetes sufferers. One study on type 2 diabetes showed an improvement in insulin resistance with L-carnitine supplementation—though it was combined with a calorie-restricted diet. When compared with the placebo group, those given L-carnitine saw plasma insulin levels and overall insulin resistance significantly decrease.9
Brain Function And Dementia
Acetyl-L-carnitine, another form of carnitine, has been shown to decrease brain deterioration in those suffering from Alzheimer’s disease. It’s thought that carnitine improves cognitive function by reducing or blocking the neural death of cells common in patients with dementia. More studies, however, are needed.1
The skeletal muscles and heart contain the highest concentrations of carnitine in the body. They get this compound from blood plasma and cannot synthesize it themselves. Because of this, the heart and muscles can be especially affected by carnitine deficiencies.
For those with cardiovascular issues—such as chronic heart failure or coronary heart disease—L-carnitine supplementation can increase blood flow and reduce high levels of free fatty acids that could damage the heart. It’s thought that L-carnitine supports the metabolism of cells in the heart as well as restores its energy reserves.1
Additionally, one study showed that L-carnitine lowered blood pressure and reduced inflammation in rats. Taking a balanced supplement that includes L-carnitine and other beneficial nutrients—such as ecoNugenics Circutol—can support circulation and healthy blood flow that is essential for cardiovascular health.*10
Is L-Carnitine Safe?
According to research, supplementing with L-carnitine up to 2-3 grams daily is considered safe and non-toxic. Of course, it’s always important to check with a doctor before beginning any supplementation regimen, as there may be certain conditions negatively affected by L-carnitine supplementation. Overall, L-carnitine is an essential compound that balances metabolism and energy production in the cells and plays a key role in overall health.1
- Flanagan JL, Simmons PA, Vehige J, Willcox MD, Garrett Q. Role of carnitine in disease. Nutr Metab (Lond). 2010;7(1):30.
- Traina G. The neurobiology of acetyl-L-carnitine. Front Biosci (Landmark Ed). 2016;21:1314-1329.
- Bloomer RJ, Tschume LC, Smith WA. Glycine propionyl-L-carnitine modulates lipid peroxidation and nitric oxide in human subjects. Int J Vitam Nutr Res. 2009;79(3):131-141.
- Spiering BA, Kraemer WJ, Vingren JL, Hatfield DL, Fragala MS, Ho J-Y, Maresh CM, Anderson
- JM, Volek JS. Responses of criterion variables to different supplemental doses of L-carnitine L-tartrate. J Strength Cond Res. 2007;21(1):259-264.
- Rebouche CJ. Effect of dietary carnitine isomers and gamma-butyrobetaine on L-carnitine biosynthesis and metabolism in the rat. J Nutr. 1983;113(10):1906-1913.
- Pooyandjoo M, Nouhi M, Shab-Bidar S, Djafarian K, Olyaeemanesh A. The effect of (L-)carnitine on weight loss in adults: a systematic review and meta-analysis of randomized controlled trials: Carnitine and weight loss. Obes Rev. 2016;17(10):970-976.
- Brass EP. Carnitine and sports medicine: use or abuse? Ann N Y Acad Sci. 2004;1033(1):67-78.
- Giamberardino MA, Dragani L, Valente R, Di Lisa F, Saggini R, Vecchiet L. Effects of prolonged L-carnitine administration on delayed muscle pain and CK release after eccentric effort. Int J Sports Med. 1996;17(5):320-324.
- Molfino A, Cascino A, Conte C, Ramaccini C, Rossi Fanelli F, Laviano A. Caloric restriction and L-carnitine administration improves insulin sensitivity in patients with impaired glucose metabolism. JPEN J Parenter Enteral Nutr. 2010;34(3):295-299.
- Miguel-Carrasco JL, Mate A, Monserrat MT, Arias JL, Aramburu O, Vázquez CM. The role of inflammatory markers in the cardioprotective effect of L-carnitine in L-NAME-induced hypertension. Am J Hypertens. 2008;21(11):1231-1237.